Inertia controlled pilot apparatus



March 24, 1953 l Lf-B. LYNN 2,532,455

INERTIA CONIROLLED PILOT APPARATUS Filed Feb. 21, 1948 .2A SHEETS-SHEET2 Patented Mar. 24, 17953 INERTIA CONTROLLED PILOT APPARATUS Lawrence B.Lynn, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation,East Pittsburgh, Pa., a corporation of Pennsylvania,

Application February 21, 1948, Serial No. 10,162

Claims. (Cl. 137-45) My invention relates to inertia controlled pilot iapparatus for stabilizing equipment such as ride stabilizers onconveyances. In a more particular aspect, my invention involves inertiacontrolled pilot apparatus with valves for the control of hydraulicpower` systems of the type disclosed in the copending applicationsSerial No. 509,314 of C. R. Hanna, now Patent No. 2,492,990 of January3, 1950, Serial No. 623,368 of L. B. Lynn and C. R. Hanna, now PatentNo. 2,568,401 of September 18, 1951, Serial No. 794,145 now abandoned,of L. B. Lynn, and Serial No. '787,230 now Patent No. 2,520,944 ofSeptember 5, 1950, of L. B. Lynn and S. J. Mikina, all assigned to theassignee of the present invention.

Pilot apparatus of the kind here concerned perform a controlling actionin response to oscillating forces or movements in predetermined planesor directions. The sensing element proper consists of an inertia membersuch as a pendulous or spring suspended mass, that is biased to normallyremain in a center position and denects to either side in response tothe occurrence of movement to be stabilized. In the pilot apparatusdisclosed in the above-mentioned applications, the inertia member servesto actuate two valves of a hydraulic system so that the deflectionof theinertia member causes an increase in the ow area of one valve and asimultaneous decrease in the area of the other thus producing acorresponding pressure difference between two ducts controlled by therespective valves. The valves are interconnected and are exposed topressures resulting from the controlled Huid flow. The pressures on thevalves are normally equal and hence impose another centering bias on thevalve assembly and on the inertia member connected therewith. Y

' However, there are phenomena that tend to disturb the centering orbalancing bias. For instance, when a vehicle equipped with an inertiacontrolled stabilizer is passing through a curve, a bias due tocentrifugal force is superimposed Von the spring bias of the inertiamember `and causes the member to deilect steadily toward one side of thenormal center position. Other unbalancing effects may occur due tounequal thermal expansion of the valve structure, fatigue,

,and thermal creep of the centeringsprings of the According to theabove-mentioned copending application Serial No. 623,368, detrimentaleffects of such an unbalancing bias are prevented by providing anautomatic re-centering device which, in response to a steady unbalanceof the controlled valves, shifts the abutment of a centering spring inthe direction required to compensate for the steady unbalancing inuence.The present invention is also intended to automatically compensate suchdetrimental effects but aims at Aachieving this object by means ofgreatly simplified design. i

My invention is based on the fact that the above-mentioned unwantedeffects are all relatively slow as compared with the cyclical Vdisiturbances intended to be stabilized, the latter of discriminatingbetween high frequency movements to be transmitted and low frequencymovement to be eliminated. This requires that the valve actuatingstructure or other element to be controlled by the inertia member bemovable independently of the inertia member. It is also necessary toapply a centering bias to the controlled element independent of thecentering bias of the inertia member, although, if theinvention isapplied to differentially acting balanced valves of the kind disclosedin the above-mentioned copending applications, such an independentcentering of the controlled (valve actuating) element is inherent in thepressure-balanced valve design so that separate biasing springs for thecontrolled element are not required.

An embodiment of the invention is illustrated in the drawings, in which:Y

Figure 1 is a hydraulic circuit diagram of a stabilizing systemcontrolled by an inertia responsive pilot apparatus according to theinvention, while Figs. 2 to 6 show details of the pilot apparatus; moreparticularly, 1

Fig. 2 is a cross section through the pilot apparatus taken along aplane denoted in-Fig. 3 by the line II-II,

Fig. 3 is a cross section taken at a right angle to Fig. 2 substantiallyalong the center plane of Fig. 2,

Fig. 4 is a section at a `right angle to Fig. 3 along the plane denotedby the line IV'IV in Fig. 3,

Fig. 5 is a view of part of the apparatus from the right of Fig. 3, and

taken Fig. 6 is a section through a detail of ther trolled by thedifference the' priessies apff" plied to a pair of ducts or' eon'niits'Vft2', l

Liquid under pressure is provided by* a positive V displacement pump iMwhichfhas areturn duct and a pressure duct |06. The pressure duct w3 issplit into two branch conduits lb andi lllEc. Disposed between pump |54and controlled device lill isfa pilot apparatus |31 whose housingstructure has two cavities |38 and |031 Cavity |18 has two'valveopenings and H3 in communi'cation with the respective pump ducts lii'band' |635y and. controlled by two valvel faces of a valve body |22.Cavity |09 has two'valve open ing-s I l5 and' il l in. communicationwithconduits |030 and |95,- respectively, and controlled by valve facesor afvalve body |23: The bodies |22 and |23 are interconnectedby arodli;v The control-.device or pilot apparatus HH encloses a-neu-ftralpressure space |29 which` is in free communicationlwith thefreturnconduit It?? and with the vvalve openings' |!3 and An inertia weight |25is movably suspended within the neutral pressure space |23-, Weight |25is mountedonan arm |23 which is pivotedabout a shaft |21l andlinkedstorthe Gonnectingrodl |24. The weight |25 isnormally heldlintenter position by means of a-biasing spring 28A.-

Another arrn` |23` is pivotedV about shaft |22 and linked to rod |24. Amechanical nlter |22 ofthe dash-pot type has acylinderl attached toweight arm |23 and a-piston linked toarm |23. As will ibe'explainedbelow,.the` filter |29`behaves as ifit were a rigid connection betweenarins |25E and- |26 when thev weight perfor'rn'sY rapid oscillations,but the' ilter |29 yieldsfto-slo'w' movenients andfhenc'e perm'its'acentering' adjustment of arn |23 independent frein the centeringadjustmentof erm |25'.

The controlled stabilizing device lill has a cylinder with tw'o pistons|30V and |3| which form, togetherjwith the cylinder, two pressure spaces|32 and |33, respectively, and anY intermediate neutral space |313'.Ifhe neutral space is connected by Aa conduit |35` witnth'e' neutralspace |2i of the control deviceV |31 and with the'v return conduit' |35lof the pm'p'. The neutral space i3d of device" ||l| is traversed by ashaft |33 which carries a cylindrical transmitting member |31. Member|31 is engaged. by the two pistons lst and |34. An arm ist is mounted onshaft |36 outside o'fdevic'e' fill.

For the purpose of enplanation, it may beassuined that the entirehydratant' system of Fig. 1 is mounted on the spring-supported bodyv ofa vehicle so that the plane of illustration represents.-avertical-plaineV of the vehicle body, the travelling direction of thevehicle being per-pendicular to-the plane-of illustration.l I-t mayvfurther be assumed that the apparatus serves for stabilizing verticaloscillations of the vehiclebody, and that the peripheral endiof arm |38is linked to the unsprung mass.` of the'vehicl'efas: is'- sche- Itconsists of a cylinder-andi" matically represented by a broken line |43connecting the arm |38 to the journal structure |4| of the vehicletruck.

A vertical movement of the vehicle body relative to space, for instancein the upward direction, has the effect of causing a relative movementbetween the weight |25 and thehousing structure of the pilot apparatus.'EI-iat is, weight |25 tends' to' maintain its original position inspace and hence moves downward relative to the upwardly acceleratedhousing structure. When this movementis fast enough to :be transmittedthrough theY lter |29, the valve structure is lifted so thattthelflowareas of Valve openings and |123* and |15 areincreased. As a result,the pressure in oavityd, duct |02 and pressure space |32 is rreduce-'3., and the pressure in cavity |89, duct' |53 and pressure space|33 .is increased. The previously balanced piston assembly of the deviceis shifted in the upward direction so that arm |33 is turned- Vclockwise, i. e., also in the'upward direction. Hence, arm |3Bvand link|40 pull the vehicle body downward toward the unsprung vehicle structure|4| and counteract the moving tendency of the body. In this manner, thesystemV is effective toprevent or diminish any verticalV oscillations ofthe vehicle body.

fis-mentioned above, the mechanical filter |29 transmits any fastoscillations of theweight to the valve structure but yields to slowmovements as may be caused by the effects of centrifugal force or by anyother persistent delecting bias acting on the weight orY on the normallybalanced valve structure.A How this discriminatory nlt'er action vcomesabout' will be understood from the following description of the pilotapparatus shown in detail in Figs. 2 to 6.

The pilot apparatus according to Figs. 2' to 6 contains a number ofducts, passages, cavities and other enclosed chambers or' spaces whichare formed by livev bodies 2ill, 232, 263, 20d; 255. These bodies arenrmly and tightly attached to each other and form together a rigidhousing and a support for a number oi elements described hereinafter.

Bodies and' 233`-liave an entrance chamber tor 23d (Fig. 3) closed by a'cover screw 268 or 239i Each entrancechambe'i has a threaded openingatwh'ich'the'pump'outlet conduit mtb or lecl is`= attaclfied.v Sleeves212' and 213i are in'- s'erted in' bodies 202 and' 203', respectively,and have' each. acav'ity les cime'. Cavity les communicates through avalve Opening with the entrance cha'rhbe'r 203 hence withl the conduit|6517 (Fig. 3l. Cavity |891 communicates through a valveopening with thechamber 2D? and hence with` the conduit lltcwhich leads to the same pumpoutlet duct as the conduit F0612. Sleeve 212 has another (lower) Valveopening through which the cavity' F33 (Fig. 3) communicates withv an Yintermediatev pressure chamber 2|4 which, in turn, c`omrnunicates withthe neutral pressure space |26 within body 205 in a manner to beAdescribed in ya later place; and cavity' |39v (Fig. 3) has another'(upper) valve opening. in' communication with' another intermediatepressure chamber 2|5` also in hydraulic connection with' the neutralpressure space |2`l. Two valve'bodies- |22 and 23` are movableA in therespectivecavities; Each of'bodies |22 and |23 has two valvefaces*tocooperatewith the respec; tiveY two'valve' openings'l of eachcavity (as explained-above with reference' to Fig. 1').

Across bore 2|f|fin body 232 (Fig. 6) is in-free communication withcavity |09 andvis-pluggedat 'valves (pilot valves) 266 and 251.(Fig. 3).

5 one end. The other end of bore 2 l1, selected for most convenientinstallation, receives the end of conduit |02 leading to the controlleddevice |0| (see Fig. 1). The design of body 203 (Fig. 3) is similar tothat of body 202 shown in Fig. 6, except Vthat the cavity |09 in body203 is in free comof the conof the` controlled device.

The two intermediate Vpressure chambers 2|@ and 2| 5 (Fig. 3)communicate with each other through bores 223,224, 225 (Figs. 2, 3) ofbody 20|. Bore 225 communicateswith bores 222 (Fig. 2) under control `bya spring biased pressure-control valve 22,6,adjustable by means of `ascrew 221. Valve 226 checks the iiow f liquid from bores 222 to theintermediate pressure chambers 2|4, 2|5 but permits a iiow in thereverse direction if the pressure in the intermediate chambers exceedsan adjusted value.V Hence, the setting of valve 225 determines thepressure difference maintained between the intermediate chambers Zhi,

A 2|5 Aand the neutral space |20.

The inertia weight |25 is mounted on an'arm |25, whose pivot shaft|21vis journalled in ball Vbearings mounted on body-234 (Figs. 2, 3 and4).

The centering spring |28 for weight A|25 rests against an abutment 233which is in threaded engagement with a screw 235 mounted on` body 205.The abutment is set for adjusting `and roughly balancing the `centeringforce of spring` |28. A correct balance is secured by shifting the screw235 with the aid of a Calibrating screw `23.5 threaded into a bore ofbody 205 and accessible from the outside after removal of a cover screw231 (Fig. 4). n The valve bodies |22 and |23 are mounted on rods 242 and243, respectively (Fig. 3). The rods are attachedV to respective pistonstructures 2M and 235 which are movable in cylinders 240 and 241, andhave cup-shaped packings 248 and 243, respectively. The two pistonstructures are interconnected'by struts 25|, 252, 253 (Figs. 2, 3) whichpass through the respective bores 223, 22d and 225. Consequently, thetwo valve bodies |22 and |23k form part of a rigid valve structure andmove in unison in the same manner as explained above with Vrespect toFig. 1.

The just-mentioned cylinder-and-piston devices disposed in theintermediate pressure cham- `bers2|4 and 2 I5 represent variable-volumecontainers for actuatingthe valve structure. Each of cylinders 246 and241 communicates through an orifice 256 lor 251 with the intermediatepressure chamber 2| 4 or 2|5 and has an outlet passage in communicationwith ,a duct 253 or 259 of body 20| (Fig. 3). i Ducts258 and 259 openinto cavities 262 and 263,v respectively (Figs. 3, 5), which areconnected with the neutral space |23 through respective orices 254 and265.v The flow areas of these orices are controlled by poppet The twopilot'valves are controlled in inverse relation to each other by ateeter bar 268 which is pivoted about the shaft |21 of the weight arm|26` but journalled in Vseparate bearings 239 and 210 (Fig.

weight |25. The frequencydiscriminatinglten denoted as a Whole by |29 inFig. 1, comprises a dashpot cylinder290 and apiston 29| with a cup-typepacking. Cylinder 290 is iirmly secured to the weight arm |26, andpiston 29| has a piston rod 29,2 linked to the teeter bar 268- (Fig. 3).The cylinder 290 has a capillary leak formed by a capillary tube 233whose cross section and length are chosen in accordance with the desiredtime constant. Cylinder 290 is filled with liquid and communicatesthrough tube 293 with the liquid-lled neutral space |20.v The dash-potlter` transmits forces between weight arm and teeter bar in proportionto the relative velocity of cylinder and piston. The dash-pot volume andthe capillary tubes are proportioned so that this velocity is very lowfor the maximum required valve force. The eifect of the filter on thesensi tivity of the pilot apparatus is therefore negligible.` Fastoscillations of the weight |25 are transmitted, without appreciableloss, to the teeter bar so that the latter follows oscillationresponsiveweight movementswithout delay and through the entire range of movementwithout appreciable slipping. When the weight and the teeter ,bar arenot affected by oscillations to be responded to, the weight is centeredby its` own spring bias to the proper center position, and the teeterVbar is independently biased toward its center position due to thenormally balanced biasing forces due to the jet stiffness of the pilotvalves 266 and 261, the degree of accuracy of this centering bias beinglimited only by the friction of the teeter bar bearings and the frictionof pistor 29| in cylinder 200. Any steady influences, tending to holdthe weight of the teeter bar deflected from the normal center position,are not transmitted through the. filter because the lter yields to theslow movement caused by such phenomena. For instance, if the teeter barshould become deiiected from the normal center position, the filternevertheless permits the weight to remain independently centered or tobecome re-centered by its owncentering bias. In this manner, the lteroperates as an automatic re-centering device.'

Considering in the following only the response to fast oscillations withrespect to which the filter maylbe 'considered a rigid link betweeninertia member and pilot valves, the pilot apparatus as a whole operatesinthe following manner.

Whenthe weight |25 and the pilot valves are in the illustrated centerpositions, the flow areas of the two pilot valves are equal. Thenpressure obtaining between the orices 256 andV 264, i. e., withincylinder 246, is equal to the pressure obtaining between the orifices251 and 265, i. e., within cylinder 241. Consequently, the force imposedby the pistons 244 and 245 on the valve structure are balanced,`and thevalve structure is normally in the illustrated centered position. Whenthe inertia weight deflects from the center position, one pilot valvereduces its ow area and the other increases its flow area. The pressuresin the cylinders 246 and 241 become different from each other so thatone piston moves inwardly and the other, outwardly of the appertainingcylinder. lAs a result, the valve assembly moves one or the other awaydepending uponthe direction of Weight deflection.v The hydraulictransmission between the inertia weight and the compound main valvesrepresents a power multiplying or amplifying system. That is, smallvariations in force or displacement imposed on the pilot valves causeproportionate variations of 2) -and hence movable independently of the75 amplified forces or displacements Vto occur at tiret rliaiiiLvalve's- Hence; theL dey-icel according tol 2 to 6'I provides:amplification inl addition to that inherent-ini thehydrauiicsystem-foff' the :nain:valves.v Itrnay'be' mentioned-hdwever; that fof-'many'-purposes;includingl the control ofstabilizing equipment,` theamplication obtainable by the' main` valve systern is# sunici'entso1that the fltene'iementf I29 may' bev directly linked"v to the:tira-in@valve` structure thusf-p'erinitting aconsiider'-ablesiniplicationl of; the` device@ (see Fig v 1)-.

For inertia cor-n-olle'dt vehicle stabilizing equip# ment aii controlperformanceproportional tothe velocity' ofi the movements! tobe'stabiliized is usually? desirablei Since the irieveineiits of' aninertia weight-l relative to its supporti areAJ pro"-V pii'tional teacceleration i'f` theL weight-l subjee/ted to an elastid bias only;darnp'rigfiiieans arel provided t'oreceive the preferredvelocityproportionaldeflection;- 'Iih'ese' damping means,`a'sshown'-Fi'g. 3, are disposed and designed inthe following manner.

ody 2154 has'v two coaxialb'o'res 2552*' and@ 27% which form dashpotcylinders and are covered by respective platesl 2li?" and; 215i Eachplate has an oriiice'fZllior ZH. Pistonsi'i Zilv'vith cup=shaped1packingsare' movable in the cylinder's and are rigidly interconnected bya r'od 283. Rod- 28p' passes` thro'ueh ari' opening in weiglitarin i215*(Figs: 2,; S'andfi'sipivotally linked to arm I 2tby" a` shaft 2581.Cylinders 2512` and 21113?coininunicate'through an orifice 2355V or 283and a' duct 23e or 2tewith a cavity 25kt or 23'! (Figs 3", 5) which ishydraulically connected to ther intermediate pressure chamber 2li? or'2i5 (Fig. 3'): Hence, there is a steady ow'of liquid from' chamber 2Nthrough a' bleeder passage 286L;28`1l-`28`2'-\212;2l6t0` then'eutralpressure space 120'; A' similar bleeder passage 23T- 285'-2'33l-'2'!3"-2 leads from' intermediate pressure chamber' 2te' toneutralv space |211'. Any movenient of weightA 25 about itsl centerpositionY causes thedamper pistons 278'v and 219`to" reduce the''er'icio'sed volumeJ or one cyiinderfand to' increase' that" or' theother cynnder.' The expand'- ingcylinder space draws` liquid' throughthel orificeszt, Zwar-271;, 283 and' the compressed cyliiideispaceeripelsv liquid' through the* respective orifices so" that the' piston'movements are damped; oreorince'ofeacri' cylinder the' flow componentdue` to pisto'rirove inthe' direction' of the steady" 'flow froin the"Iintermediateprs'sure chamber' to the neutral space, while i theothe'ioric thetwo ovv Components are opposition' tol each other.Underthese conditions the' daipillg effect iS independent of the furthereffects' that the damping force iSV substantially' proportional to thepiston movement, that the cylinders are automatically filled when thesourceV of pressure liquid is putin operation; and that any initiallyenclosed` air bubbles are scavengedout' of the? cyiinden Be'-Y sidesg-byadjusting' or! selecting the flow" resist;

ance'of the bleederlpassages'arid orificesso'f that theavera'gepressurein. thecylinder isnot higher than: the meanivalue of the modulatedpressure, the leakage. losses` and theVVV friction at the cupshaped.Ipackings can be" keptata rhinin'iunif Duel-to the steady iiow' of liquidtromlthefin'termediate pressure chambers 211i; 21'5 (Fi'gBJ to theneutral space IZl through the; bleede'r" pasages oftheactuatingcylinders-2146, zlllgthejlatter cylinders are' alsoscavenge'dby a steady flowv of liquid and thel force impartedV toltheirrespective pistonsV is proportional to: the pressure: variation or'movern'entfoi. thepilot valves. In ordeitoreduceleakagelosses andfriction atthecup-type packings 248, 2'49 theaverage'pressure' Withinthe actuating cylinders may also be adjusted' to be not appreciablyhigher than the mean modulated pressure'.

While. I have ex'einplied my inventionby anembodiment vvotlierv/isebased on. features disclosed inl the aboveernentioned application;Serial No. 787,230, it canreadily bei applied topi1ot' apparatus asfshown in the above-mentioned other applications as well as tol any otherinertia-'controlled pilotapparatusregardlessY of whether the controlledsystem ishydraulicf, electric or otherwise andi whether the inertia'member` is a rela# tively movable mass ora gyroscope'.v In other words,apparatus accordingVVA to the invention can be modied in variousrespects' and may be real-V ized by structural embodiments other thanvthose specifically illustrated anddescribedg Without departing from theessence or the invention and within. the essential` features ofl theinvention set forth in the claims'annexed hereto.

I claim' asmy invention:-

1. An inertia. responsive control? apparatus, comprising av support, twovalves a-teeter bar having a pivot shaft mountedon said support andhavingY two arms associated with said valves respectively forcontrolling' thezn inverse re'- lation to each other, an; inertia weightpivoted about the axis of said'L shaft, spring means disposed betweensaid support and said-weig'ht for biasing said weight toward-a norrnal-`positionyand a dash-pot device havingI two relatively movable membersforming together a variable volume chamber and being attached-tosaid-weight and said toeter bari respectively; said devicel'having acapillaryVv duct through which saidfchar'nber-cornmunicates with theexterior spa`ce",- and-alhousing for liquid enclosing said teetervb'a'rfand saidweight andsaid device.

2. An inertia responsive control apparatus, comprising a support, twovalves",` amovablelniember connected to both of the twofvalves andmovably n'iounted onv said-support for 'controlling said valves ininverse relation'tofeach other, an inertia weight movably mounted on'-said support,y spring means disposed between saidsupport and saidweightA for biasing-v s'a-i'd `weight toward a' normal positioni and'adashpot device havingA two-relatively movable members forming togetheravarie abley volume chamber and being attached to said weight and saidmovable member' respectively; said. dashpot device having' Va'- slfnallopening therein through which said chamber communicates with theexterior`v space, and-a housing for liquid enclosing said movablemember" and said weight andy saiddashpot device.

3i In an apparatus responsive to vertical movement of a conveyance, thecombination of,.a support, a member tobe controlledrmovably mounted onsaid support andlyieldably'restrained` ina predetermined posi-tion;y apassive massi movably mounted on said support for movement in asubstantially vertical plane, a spring subject to creep yieldablysupporting said mass in said vertical planeA and urging said mass to agiven position, said mass being movable from said given position uponacceleration of said support in the plane of movement of said mass,coupling means connecting said mass to said member to be controlled toactuate said member from its predetermined position, said mass beingalso ldisplaceable from said given position upon the occurrence of creepin said spring, and a dashpot device forming a part of said couplingmeans to permit movement of said mass from said given position to a newposi- -tion with creep of said spring without displacing said member tobe controlled from its predeterminedposition. Y

4. In stabilizer apparatus, a passive inertia control member, meansmovably supporting said inertia control member for movement in a given`plane, spring means biasing said inertia control member to a givenposition, said spring means being subject to drift due to fatigue andpermitting displacement of said control member from said given position,a controller device adapted for actuation by said inertia control memberupon movement thereof in said given plane, and dashpot means connectedbetween sai-d inertia control member and said controller devicetoactuate said controller device and -to compensate said drift of saidspring means.

5. In stabilizer apparatus, a pick-01T device having a member movablefrom a neutral position for controlling said pick-01T device, a passiveinertia control element, means movably supporting said inertia controlelement for movement in a given plane, spring means subject to creepyieldably biasing said inertial control element toward a given position,coupling means connecting said inertia control element to said member toactuate said member from its neutral position upon displacement of saidinertiav control element, and dashpot means included in said couplingmeans and connected between said member and said inertia control elementto permit movement of said inertia control element'from said givenposition to a new position ,with creep of said spring without displacingsaid-"member from its neutral position.

B. LYNN.

REFERENCES CITED The following references arej of record in the flle ofthis patent: .4

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